1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a dual liquid crystal display device comprising a first transmissive liquid crystal display panel and a second reflective liquid crystal display panel.
2. Description of the Related Art
A liquid crystal display device is a flat panel display having advantages that it is manufactured in a small and thin scale and driven with low power consumption, and therefore it has been used in portable computers such as notebook PCs, office automation equipments, audio/video equipments, etc. Examples of such devices are as follows:
U.S. Pat. No. 7,193,666 to Jung-Min Choi et al. and entitled DUAL LIQUID CRYSTAL DISPLAY DEVICE describes an LCD device for performing bi-directional display. The LCD device includes first and second display units, and a light supplying unit. The first display unit includes an LCD panel and a transflective film that is disposed under the LCD panel and has layers in which first and second layers having different refractivity indexes are alternately stacked. The transflective film partially reflects and transmits light incident onto the film. The light supplying unit is disposed between the first and second display units, and provide the first and second display units with light generated from a lamp by dividing the light, to thereby regulate a contrast ratio of a luminance between the first and second display units;
U.S. Pat. No. 7,075,597 to Chi-Jain Wen et al, and entitled DUAL-SCREEN LIQUID CRYSTAL DISPLAY discloses a dual-screen liquid crystal display including three substrates. The first substrate has a first surface and a second surface. The first reflector layer, the first liquid crystal layer, the second substrate and the first polarization film are sequentially disposed on the first surface of the first substrate to form the first reflective LCD. The second reflector layer, the second liquid crystal layer, the third substrate and the second polarization film are sequentially disposed on the second surface of the first substrate to form the second reflective LCD; and
U.S. Pat. No. 7,034,799 to Seog-Geun Lee et al. and entitled BACKLIGHTING DEVICE FOR DUAL LIQUID CRYSTAL DISPLAY AND FOLDER-TYPE MOBILE PHONE THEREWITH describes a backlighting device for a dual LCD (Liquid Crystal Display). The backlighting device includes a circuit board with a through hole; a backlighting illumination device situated within the hole for radiating light in a first direction substantially perpendicular to a first face of the circuit board and in a second direction substantially perpendicular to a second face of the circuit board; a main LCD being situated on one face of the backlighting illumination device in the first direction, for displaying first information in the first direction; and a slave LCD being situated on another face of the backlighting illumination device through the through hole in the second direction, for displaying second information in the second direction.
A liquid crystal display device functions to display a picture or an image by controlling an electric field to transmit or cut off light, the electric field being applied to liquid crystal materials having dielectric anisotropy. The liquid crystal display device uses an external light without generating light by itself, unlike display devices, such as an organic light emitting display device (OLED) and a cathode ray tube (CRT), that generate light by itself.
In general, the liquid crystal display devices are mainly divided into transmissive and reflective liquid crystal display devices, depending on the manners of employing light.
That is to say, the liquid crystal display devices are divided into a transmissive liquid crystal display device and a reflective liquid crystal display device, depending on whether it uses a separate backlight unit or reflected external light as its power source, and there has also been an attempt to develop a transflective liquid crystal display device in which a transmissive liquid crystal display device are combined with a reflective liquid crystal display device.
Also, a dual liquid crystal display device displaying a picture on both sides of a liquid crystal display device has been developed recently. The dual liquid crystal display device display a picture on both sides thereof since it includes a main liquid crystal display panel and a sub liquid crystal display panel, both of which are formed on both sides thereof, respectively.
However, conventional dual liquid crystal display devices have disadvantages that they are thick and heavy, and their power consumption is high since a backlight unit needs to be installed for each of the main liquid crystal display panels and the sub liquid crystal display panels.
This trend runs against small and thin portable devices such as mobile phones using a liquid crystal display device, and therefore the liquid crystal display device has major problems in aspect of slimness and cost efficiency.